Data offload generally refers to a transfer process of data that is temporally stored on a physical medium, such as a Network video recorder, to a desired destination upon detecting a suitable connection for the data transfer. The offload can be carried out wirelessly or with wired connection. The use of complementary or dedicated technology for the data offload purposes is especially advantageous in a situation where the data network resource allocated for the data delivery is about to reach its maximum capacity.
A specific challenge in wireless data traffic is the data delivery to and from mobile vehicles, especially public transportation vehicles, like trains, trams, metro trains and busses. A moving vehicle, as such, poses challenges to reliable data transfer, where the usable data rate typically reduces as a function of the speed of the vehicle. Many public transportation operators have started to offer a wireless data connection, such as a Wi-Fi connection, for the passengers to use during their trip. Moreover, the requirements for using video surveillance in public transportation vehicles are continuously increasing. The video data from a plurality of surveillance cameras, together with the data traffic of the passengers, easily amounts to an extensive quantity of data, which cannot be transferred within the capacity of current wireless networks without a significant delay.
In public transportation vehicles, the wireless offload is typically carried out when the vehicle stops, or at least slows down, at a predetermined location, such as a train station or a bus stop. Wireless offload system of the vehicle may include several clients which perform wireless offload simultaneously with a plurality of access points located at said predetermined location. The clients aim to connect to an access point offering the strongest signal. This easily leads to a situation, where all clients of the vehicle try to connect to one or two access points offering the strongest signal, while no client tries to connect to the remaining access points. In other words, the available bandwidth of all access points is unevenly utilized and non-optimally shared between the clients, and subsequently all clients sharing the same access point experience poorer performance of wireless offload.